Parents: Daughter manipulated by accused killer of Westborough teen

The parents of Kathryn “Kat” McDonough believe that Seth Mazzaglia manipulated their daughter and prevented her from contacting them over a number of months dating back to March, the family's lawyer said Wednesday.

The parents of Kathryn “Kat” McDonough believe that Seth Mazzaglia manipulated their daughter and prevented her from contacting them over a number of months dating back to March, the family's lawyer said Wednesday.

Portsmouth residents Denise and Peter McDonough “are living a nightmare. They are living a parental nightmare,” Portsmouth attorney Jay Nadeau told the Herald in an interview.

Kathryn McDonough, 19, charged with lying to investigators about her whereabouts the day Elizabeth "Lizzi" Marriott, a 19-year-old University of New Hampshire student from Westborough, Mass., was killed, waived her right Wednesday to have prosecutors detail the evidence against her.

McDonough appeared in Portsmouth District Court and again agreed to conditions of her release on $35,000 bail. Those conditions include an order that she have no contact with Mazzaglia — the man charged with second-degree murder in the death of Marriott.

The McDonoughs hired Nadeau after their daughter was arrested on Christmas Eve on charges alleging she lied to police investigating the disappearance of Marriott, a marine biology student at UNH.

Mazzaglia, now 30, was dating and living with McDonough at his Sawyer Mill apartment in Dover prior to his arrest Oct. 13 on a second degree murder charge for allegedly strangling or suffocating Marriott on Oct. 9.

According to Nadeau, Kat McDonough moved out of her parents' home in Elwyn Park during February school vacation at Portsmouth High School, where she was a senior at the time. Denise McDonough found a note from her daughter left on her bedroom pillow when she returned home from work one day, Nadeau said.

The letter did not indicate where Kat McDonough was going, and only through some friends was Denise able to find out that her daughter had moved in with Mazzaglia.

According to a Dover police incident report obtained by the Portsmouth Herald through a Right to Know request, a Dover officer responded to Mazzaglia's apartment on March 11 around 10 p.m. for a reported disturbance in a hallway. The officer found Kat and Denise “actively involved in conversation, but not yelling.”

“I spoke with Denise McDonough, who told me her 18-year-old daughter, Kathryn McDonough, had moved out of her house and into 1 Mill St. #341 with her 29-year-old boyfriend, Seth Mazzaglia,” officer Sean Kennedy wrote in the report. “Denise said Kathryn had lied to her and she came to confront Kathryn and try to convince her to move back with her.”

According to the report, Denise McDonough understood that her daughter was 18 and was free to live wherever she chose. Kat McDonough told the officer “she was choosing to live with Mazzaglia and she no longer wished to live with her mother in Portsmouth,” the report states.

The officer closed the report by noting that the mother and daughter agreed to talk about the issue another time and not in the hallway of the apartment building, where they could disturb other residents.

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Nadeau described that March conversation as a difficult one for Denise McDonough. “There was no argument. There was a lot of tears,” he said.

According to Nadeau, when Denise McDonough arrived to confront her daughter, Mazzaglia stood in front of the doorway with his chest out and his arms crossed.

“They felt that he was blocking access for Mrs. McDonough to see her daughter,” Nadeau said. “They felt then, as they continue to feel now, that Mr. Mazzaglia, who is significantly older than their daughter, manipulated her into moving out of their home and moving in with him.”

Nadeau said Kat McDonough suddenly moving out was “shocking” and “upsetting” to her parents. He said there had been no troubles at home before she moved out, but once she moved in with Mazzaglia, she cut off all contact with her parents.

The parents had never met Mazzaglia before that March 11 encounter, but Kat McDonough may have been dating him from the time she was 17 years old, he said. He said the parents did not know anything about their relationship.

Mazzaglia has a black belt in karate and acted and choreographed fights for Seacoast theater productions. Kat McDonough also was involved in the local theater scene, and they appeared together in a 2011 production of “Last Rites” at Players' Ring in Portsmouth.

“She was under his power, his manipulative power,” Nadeau said. “That's their opinion. They felt that then, and they still feel that way today.”

Despite the falling out and the lack of contact between Kat McDonough and her parents in the months that followed, they helped her post her $35,000 cash or corporate surety bail and have accepted her back into their home as a condition of her release from jail.

“This has been a nightmare for the McDonoughs. They love their daughter very much,” Nadeau said. “They're happy that she's home. They wish it wasn't under these circumstances, but they're glad that she is back.”

Joey Cresta is a reporter for the Portsmouth Herald and seacoastonline.com.